Pérez Oscar E, Carrera Sánchez Cecilio, Pilosof Ana M R, Rodríguez Patino Juan M
Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria (1428), Buenos Aires, Argentina.
J Colloid Interface Sci. 2009 Aug 15;336(2):485-96. doi: 10.1016/j.jcis.2009.04.011. Epub 2009 Apr 12.
The aim of this research is to quantify the competitive adsorption of a whey protein concentrate (WPC) and hydroxypropyl-methyl-cellulose (HPMC so called E4M, E50LV and F4M) at the air-water interface by means of dynamic surface tensiometry and Brewster angle microscopy (BAM). These biopolymers are often used together in many food applications. The concentration of both protein and HPMC, and the WPC/HPMC ratio in the aqueous bulk phase were variables, while pH (7), the ionic strength (0.05 M) and temperature (20 degrees C) were kept constant. The differences observed between mixed systems were in accordance with the relative bulk concentration of these biopolymers (C(HPMC) and C(WPC)) and the molecular structure of HPMC. At short adsorption times, the results show that under conditions where both WPC and HPMC could saturate the air-water interface on their own or when C(HPMC) > or = C(WPC), the polysaccharide dominates the surface. At concentrations where none of the biopolymers was able to saturate the interface, a synergistic behavior was observed for HPMC with lower surface activity (E50LV and F4M), while a competitive adsorption was observed for E4M (the HPMC with the highest surface activity). At long-term adsorption the rate of penetration controls the adsorption of mixed components. The results reflect complex competitive/synergistic phenomena under conditions of thermodynamic compatibility or in the presence of a "depletion mechanism". Finally, the order in which the different components reach the interface will influence the surface composition and the film properties.
本研究的目的是通过动态表面张力测定法和布鲁斯特角显微镜（BAM）来量化乳清蛋白浓缩物（WPC）和羟丙基甲基纤维素（HPMC，即所谓的E4M、E50LV和F4M）在气-水界面的竞争吸附。这些生物聚合物在许多食品应用中经常一起使用。水相主体中蛋白质和HPMC的浓度以及WPC/HPMC的比例是变量，而pH值（7）、离子强度（0.05 M）和温度（20℃）保持恒定。在混合体系中观察到的差异与这些生物聚合物的相对本体浓度（C（HPMC）和C（WPC））以及HPMC的分子结构一致。在短吸附时间内，结果表明，在WPC和HPMC自身都能使气-水界面饱和的条件下，或者当C（HPMC）≥C（WPC）时，多糖在表面占主导地位。在两种生物聚合物都无法使界面饱和的浓度下，对于表面活性较低的HPMC（E50LV和F4M）观察到协同行为，而对于E4M（表面活性最高的HPMC）观察到竞争吸附。在长期吸附时，渗透速率控制混合组分的吸附。结果反映了在热力学相容条件下或存在“耗尽机制”时复杂的竞争/协同现象。最后，不同组分到达界面的顺序将影响表面组成和膜性能。
